1. Field of the Invention
Embodiments disclosed here generally relate to a selective completion system for dry or wet tree well. In another aspect, embodiments disclosed herein relate to a method of producing oil from a dry tree well. Embodiments disclosed herein also related to a completion system for oil produced wells or water injection wells.
2. Background Art
The control of oil and gas production wells constitutes an on-going concern of the petroleum industry due, in part, to the enormous monetary expense involved, in addition to the risks associated with environmental and safety issues. Production well control has become particularly important and more complex due to the various environments and formations in which drilling is performed. There is a need for controlling zone production, isolating specific zones and otherwise monitoring each zone in a particular well. Flow control devices such as sliding sleeve valves, downhole safety valves, and downhole chokes are commonly used to control flow between the production tubing and the casing annulus. Such devices are used for zonal isolation, selective production, flow shut-off, commingling production, and transient testing.
In wells with multiple completion zones, valves are also used to isolate the different zones. Typically, during completion of multiple zone wells, a first zone is perforated using a perforating string to achieve communication between the wellbore and adjacent formation after which the zone may be completed (i.e., allow hydrocarbons to flow into the wellbore). If completion of a second zone is desired, a valve and packer may be used to isolate the first zone while the second zone completion operation proceeds. Additional valves may be positioned in the wellbore to selectively isolate one or more of the multiple zones.
In a selective zone completion where flow from each zone is provided and controlled individually, the individual zones are separated by flow tubes. These flow tubes may have to be passed through the valves in an upstream zone to access a downstream zone. To do so, the valves are opened; for example, if flapper valves are used, they are broken by applied pressure or some mechanical mechanism so that the equipment may pass through the upstream zone to the downstream zone. Once the flapper valve is broken; however, the upstream zone is unprotected and the well may start taking fluid until the equipment has been run to and set in the downstream zone. Because zones may be large distances apart (e.g., thousands of feet), the time for the equipment to traverse the distance between the zones may be long, especially if relatively sophisticated equipment such as those in intelligent completion systems are used.
During this time, fluid pressure from the first zone is monitored to detect sudden fluctuations in well pressure which may cause a blowout condition. If well control is required, such as by activation of a blowout preventer (BOP), closing the BOP on tubing which may have cables, flat packs, and hydraulic lines attached to the outer surface of the tubing may damage the attached components and the BOP may not seal properly.
To provide better fluid loss and well isolation control, a formation isolation dual valve (FIDV) may be used. In one example FIDV, a ball valve is used to isolate one zone and a sleeve valve is used to isolate another zone. In conjunction with an isolation packer, the FIDV provides protection for multiple zones while the upper portion of the completion string is being installed.
In a multi-zone wellbore, once an FIDV and associated components are installed, a flow control device may be run into the wellbore and installed above the FIDV to perform flow control of the two or more zones during production. However, installing a separate isolation device (e.g., FIDV) for fluid loss control and flow control device adds to the complexity of completion operations. Effectively, two sets of valves are used for each zone, one for isolation and the other for flow control. Installing the extra components adds to the time and costs of completing a well. In addition, the presence of extra components increases the likelihood that failure of some downhole component may occur, which would then require a work-over operation that typically includes pulling out the completion string, replacing the failed component, and re-installing the completion string. Such work-over operations are extremely expensive and time-consuming.
Various mechanisms may be used to control activation of downhole valves. Such mechanisms may be electrically-activated, pressure-activated, or mechanically-activated. Pressure activation may be accomplished by communicating pressure through production tubing or through one or more control lines running along side the tubing. However, once production of fluids starts, communication of a desired pressure through the tubing may not be possible. Control lines may be used instead. Conventionally, separate hydraulic control lines have been used for different flow control devices. The existence of multiple control lines downhole may make installation of a completion string more difficult and the risk of damage to the control lines may increase, which increases the costs associated with the operation of a well.
The completion systems described above are typically run in subsea systems where the life expectancy of the wells is approximately 15-20 years. The components used in these completion systems are typically very robust, and therefore expensive, such that the components can withstand the high temperatures and pressures associated with deepwater systems for a long life.
A need thus exists for a completion system that is reliable and economically efficient for producing oil from land wells with marginal production.